Post Employment Plans - Net periodic pension cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	$ 3.9	$ 2.7	$ 2.5
Interest cost	2.6	2.8	3.8
Expected return on assets	(5.5)	(4.9)	(4.9)
Settlement	1.1	0.0	0.9
Curtailment	0.0	0.0	(2.5)
Net actuarial loss/(gain)	0.1	0.9	0.8
Net periodic pension cost/(gain)	2.2	1.5	0.6
Other Postretirement Benefits Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service costs	0.0	0.0	0.6
Interest cost	0.1	0.1	0.2
Expected return on assets	0.0	0.0	0.0
Settlement	0.0	0.0	0.0
Curtailment	0.0	0.0	0.0
Net actuarial loss/(gain)	(1.4)	(3.2)	(0.3)
Net periodic pension cost/(gain)	$ (1.3)	$ (3.1)	$ 0.5